Me and my brother installed a GHL 3" downpipe on his 1.8T last weekend and I snapped pictures along the way so I could do a little write up for all those wondering how it is done. It is a fairly easy procedure it just takes some time because some of the bolts are hard to get at or rusted. Here we go.

First of all you are going to need some basic tools. You need a jack and at least 2 jack stands, but I recommend 4. It is easiest to work on th ecar if the whole thing is up off the ground. You will need basic sockets and open end wrenches, a hammer or preferably a BFH (Big Freakin Hammer), and some zip ties. That is about it as far as tools.

Here is a shot of the engine bay

From here you want to look at the passanger side by the fire wall and you will see this.

That is the top of the downpipe and if you don't have a strut brace in you might be able to get at a bolt or 2 from the top side.

To start get the car jacked up and through it onto jack stands. I prefer to put all 4 corners up so you can crawl all over under the car. Now depending on your exhaust setup you may need to disconnect the whole thing or you may be able to leave it in place. With us and this Supersprint 2.5" cat back the couplet to the stock downpipe is very long and inorder to slide it off of the stock downpipe we needed to completely unbolt the exhaust.

Once the car is jacked up take this cross member with the exhaust hanger out.

Then loosen the exhaust and slide it off of the stock downpipe.

Next disconnect the down pipe from the turbo. Most of the bolts are easier to get to from the bottom of the car. I suggest taking a drop light and sticking it down from the top and shining it right on the bolts. Make sure you use plenty of penetrating lube. WD40 is not a very good penetrating lube you want something like CRC or liquid wrench, just get something that has penetrating lube written right on the front of the container. Lube these suckers up and tap on them a little to help the lube soak in. If you try wrenchig real hard on these when they are rusted (which they always are due to the extreme heat) you could break one. If you break an exhaust stud then you will be seriously screwed so take you time. We let them soak for about 15 minutes, but some let them soak for an hour or 2. They came off real easy with no struggle and the car has over 50,000 miles on it so it isn't brand new.

Here is a picture from under the car. As you can see there is plenty of room to get in there for these nuts.

Once you get it unbolted you have to manuever it out of the car. You may have to really hammer on the exhaust to get it off because it is usually crimped on from the ole exhaust clamp. Use the trusty BFH (no mechanic should be without one) and slam the hell out of the bracket that holds the exhaust to the crossmember hanger like it owes you money. Don't worry you wont bend or break that thing it should be welded on solid 1/2" rod and you can't swing that hard laying under a car in those awkward positions.

Unclip the wires that lead to the oxygen sensors so that you will have enough room to play with. We slid it just barely outside of the car and stepped on it and with an open end wrench unscrewed the oxygen sensors. We marked on of them with red electrical tape so that we knew which one went before and after the car on reinstallation.

Here are 2 pictures of the original factory downpipe and cat next to the 3" GHL downpipe and race cat. The GHL one is so big you can almost stuff you fist in it. You are going from a golf ball size to a tennis ball size.

Now installing the new pipe is reverse. thread the oxygen sensors in the correct order back into the new downpipe and bolt it back up to the turbo. I suggest using a new gasket. The shop we got the downpipe from said you coul duse the factory gasket a few times over, but when we got the old downpipe out the old gasket came out in 10 different pieces.

Here is a picture from the top of the GHL 3" downpipe installed on the car.

On the bottom side because the oxygen sensor placement is different on the GHL downpipe than it is on the factory one we used some zip ties to secure all the oxygen sensor wires to the clips that they didn't reach. Make sure they are up there real good and secure like this.

We reinstalled the Supersprint 2.5" catback exhaust and it is almost impossible to find a 3" to 2.5" exhaust reducer, but luckily GHL sells one. We ordered it from North American Motorsports and it cost another $25, but it is 304 stainless and we needed it. Now the whole exhaust system from the turbo to the exhaust tips is 304 stainless which is agood thing.

Put the reducer on, or a coupler if you have a 3" catback, loosly. Just get those hangers on. On my brother car the reducer did not want to go onto the 2.5" exhaust easily so we unbolted the mid pipe section and took it out of the car. I lined the reducer up with the midpipe and tapped it on with a hammer just to get it started. Then I took the whole midpipe and slammed that reducer on my wooden workbench a few times to drive it home with a vengence. It is times like these that make working on a car so much fun. Again the fitment issue is due to the fact that the exhaust was previously installed and the exhaust clamps that were used slightly crimped the exhaust distorting its shape enough to make this part a real PITA.

Now mate up the exhaust with the downpipe. The GHL reducer fits easily onto the downpipe you jsut have to wiggle everything around until you can move the exhaust back far enough to get a descent angle on the downpipe to get them together. The flex joint on the thing moves a good amount which makes this an easier job.

Here we had the exhaust hanging and were about to mate up the exhaust with teh reducer on the downpipe and that is when I realized that the reducer had to go onto the exhaust midpipe first then to the downpipe.

Once everything is together loosly you need to check that your exhaust tips are sitting straight and tha tall the piping is in its proper place, especially not that the section of the exhaust that goes over the rear axle beam is as far up there as it can get. Now that everything is lined up you can tighten everything back down. It is important to loose fit exhausts first, but the downpipe can be bolted tight to the turbo right away.

Now all that is left is to reinstall the crossmember with the exhaust hanger and you can drop the car and go for a cruise. You will notice the difference right away. Increased throttle response, a deeper tone, and that turbo spool up will really stick out.

It's funny how people bash the p-flow but people that bash have never actually first hand seen a intake temp log from a car with an non cai intake compared to a intake temp log from a CAI car. Honestly, performance from any intake is so minimal that a pflow vs CAI car would never be noticed even when compared to a car with a stock airbox with a stock filter. SOOOOOO many big turbo supras, DSM's, Honda's (yes I said honda's) making anywhere from 300-600whp are using an in engine compartment open airfilter on a pflow style intake and have absolutely no problems or loss of power that is measurable. Most guys that are serious about power don't even have an airfilter, simply a piece of fine screen clamped over the inlet of the turbo just sucking in hot air. It doesn't matter if the air pre turbo is even 100 degrees cooler from a CAI as compared to a pflow, it still gets heated up to a certain temp when it goes through that turbo and gets cooled to the same temp when it goes through a intercooler. There has never been any hard evidence proving otherwise.

Anyone care to provide technical data showing otherwise?

Back on topic:

Good write up. Only thing I would add is that if you think you soaked the studs/nuts on the turbo enough, squirt them again and let them soak longer. Nothing is worth the hassle of a broken stud.

It doesn't matter if the air pre turbo is even 100 degrees cooler from a CAI as compared to a pflow, it still gets heated up to a certain temp when it goes through that turbo and gets cooled to the same temp when it goes through a intercooler. There has never been any hard evidence proving otherwise.

Anyone care to provide technical data showing otherwise?

Well, no hard data here to back me up, I agree about the temp of the compressed air coming out of the turbo being basically the same temp no matter what the intake temps are. BUT, if the air going in is colder, that means you can pull more oxygen per cubic meter of air in to be compressed. No hard data though....

Back on topic...

Also the P-flo looks kind of cool, but you could build your own for about half the price.

He doesn't test the p-flow, but there is a noticable difference between the stock airbox, the CAI, and the modded airbox. I dunno if the difference in them would really make a noticable difference in HP or anything, but there is a difference...

Also the P-flo looks kind of cool, but you could build your own for about half the price.

Nice write-up.

This is my brothers car and he has never done any metal fabrication so I doubt he could pull it off. Here is my own creation on my MK3 and I think the total cost is around $40, but that includes a $9 can of high temperature paint.

The heat shield comes all the way up and presses into the hood liner to make a great seal. I noticed a definite improvement from when I had the heat shield off to when I put it back on. The first time I went for a test drive with this heat shield on I made it about 1/2 mile until a quick shift from 2nd to 3rd snapped the bolt in my front motor mount. I mean the head of the bolt sheared right off. That is good enough to convince me.

yea, the car gods were good to us that day. I thought unbolting the downpipe was going to be the worst part again the car had close to 60k when we took it off. But they came off so easily all I can say is good penetrating oil was the answer. Yes it does make the car louder especialy in cab, turbo spool up, and my diverter valve is louder not as much as what I thought, I'm happy with it. The car was noticeablely faster with throttle response, all around power, and up top in rpms even with my n75 valve going bad. Just replaced that and the combination of the 2 made a huge difference. Next step new clutch.

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